Velocity Map Ion Imaging of Chlorine Azide Photolysis: Evidence for Photolytic Production of Cyclic-N3

The method of velocity map imaging was applied to study the photodissociation dynamics of ClN3 near 235 nm under collision-free conditions. Derived kinetic energy distributions of state-selected Cl (PJ) provide a medium-resolution energy spectrum of the N3 fragment. Markedly bimodal distributions are observed that suggest simultaneous formation of the linear-N3 (X̃ 2Π) isomer as well as an energetic form of N3, consistent with recent theoretical predictions of a cyclic isomer, resembling an isosceles triangle. Angular distributions of the photofragments indicate that 21A′ r 11A′ excitation is the most important pathway to photoproducts. Branching ratio measurements between the dominant spin-orbit excited-state Cl* (P1/2) and the spin-orbit ground-state Cl (P3/2) showed Cl*/Cl ≈ 0.8/0.2. The branching ratio between linear-N3 and cyclic-N3 formation was determined to be ≈ 0.8/0.2.